JPH11126924A - Method of manufacturing gallium nitride compound semiconductor element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a metal layer on the reverse side of a substrate. SOLUTION: A separating groove 21 is formed such that it reaches a depth of approximately 15 μm on a substrate from the semiconductor side of a wafer 200 along a dicing line from an electrode side, the substrate is thinned by lapping, and a metal layer 10 is formed at a part, excluding a region B at the surrounding part of the reverse side of the substrate due to the deposition of Al (Figure (a)). Then, by dividing the wafer 200 into four portions, a wafer 201 where the metal layer 10 is formed, excluding the region B of two surrounding, adjacent sides (Figure (b)) is obtained. The separation groove 21 can be recognized visually from the reverse side of the substrate via the non-formed region B (Figure (c)), an adhesive sheet is applied to an electrode side, scribing is made from the reverse side of the substrate along the separation groove 21, and a load is applied to a wafer 201 for braking, thus manufacturing a light-emitting element where the metal layer 10 is formed on the reverse side of the substrate. Light advancing towards the substrate side from an emission layer is reflected properly by the metal layer 10 formed on the reverse side of the substrate, a light extracting efficiency from the electrode side is improved, and a high emission intensity is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a gallium nitride (Ga) nitride.
The present invention relates to a method for manufacturing a N) -based compound semiconductor device, and more particularly to a method for forming a metal layer on the back surface of a substrate.

[0002]

2. Description of the Related Art Conventionally, a GaN-based compound semiconductor light emitting device has a configuration in which a semiconductor layer is laminated on an insulating sapphire substrate, and positive and negative electrodes are provided on the same side. FIG. 8 is a schematic cross-sectional view in which the light emitting element 30 is disposed on a lead frame 31. The light emitting element 30 has a light emitting layer 34 that emits light at a predetermined wavelength, and the positive and negative electrodes 35 and 36 are provided above the substrate 33. And the substrate 3
3 is die-bonded to the lead frame 31 using a paste 32 made of a resin material.
Although not shown, the electrodes 35 and 36 are electrically connected to predetermined portions by wire bonding.
Light is extracted from the sides 5 and 36. But,
In the configuration shown in FIG. 8, since there is no selectivity in the direction of light emission obtained from the light emitting layer 34, the reflected light on the back surface of the substrate 33 greatly contributes to the light extraction amount from the electrodes 35 and 36. In addition, since light is absorbed by the paste 32 provided on the back surface of the substrate 33, there is a problem that light reflection efficiency is not good and light emission intensity is low. Also paste 3
No. 2 deteriorates with time due to ambient temperature or heat generated by driving the element 30 (discoloration to yellow), so that there is a problem that reflected light decreases and luminous intensity deteriorates with time. Further, when measuring the characteristics of the element, the wavelength and the luminous intensity are usually measured by arranging the element on an adhesive sheet, but there is a problem that the measured value is shifted because it is different from the actual mounting state. Therefore, a method of increasing the light reflection efficiency by forming a metal layer on the back surface of the substrate 33 to obtain high emission intensity is considered.

[0003]

However, since the hardness of the substrate 33 is usually large, the substrate 33 is polished and thinned when the wafer is separated, and then scribed from the back surface of the substrate 33 to form a breaking plate. The wafer 33 is separated by performing the
If a metal layer for reflection is formed on the back surface of the substrate, positioning during scribing becomes difficult. If the metal layer is formed after scribing, the electrodes 35 and 36 are formed on the wafer.
Since the pressure-sensitive adhesive sheet is adhered to the side, it is difficult to clean the rear surface of the wafer, and it is not possible to heat the metal layer at the time of forming the metal layer.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a GaN-based compound semiconductor light-emitting device, in which it is possible to form a metal layer on the back surface of a substrate, to obtain good light reflection over time, The purpose is to improve the amount of light taken out from the side.

[0005]

According to a first aspect of the present invention, there is provided a method of manufacturing a gallium nitride-based compound semiconductor device in which positive and negative electrodes are provided on the same side. In the first step, a substantially rectangular wafer having a gallium nitride-based compound semiconductor formed on a substrate is cut to a predetermined depth from the electrode side to form a first groove, and thereafter, a second groove is formed. By the above step, the back surface of the substrate is polished, and the substrate is thinned. Next, in a third step, a metal layer is formed in a region excluding at least two adjacent sides of a peripheral portion of the back surface of the substrate, and in a fourth step, the first layer is formed from the metal layer side through the peripheral portion. Visually recognize the groove of the first
Is scribed along the groove. Thereafter, in a fifth step, the wafer is broken and separated into individual devices. As described above, since the metal layer is not formed on at least two adjacent sides of the peripheral portion of the back surface of the substrate, the first groove can be visually recognized from the back surface side through this portion, and scribing can be easily performed. . Also, by forming the metal layer before scribing, the back surface of the substrate can be washed and the metal layer can be formed by heating, the adhesion between the metal layer and the back surface can be improved, and the amount of chipping during scribing can be reduced. In addition, since the metal layer has a higher thermal conductivity than the sapphire substrate, the heat generated during scribing can be radiated well,
The wear amount of the cutting blade of the scriber can be reduced. In addition, since the metal layer is formed on the back surface of the substrate, light output from the element to the substrate side is reflected by the metal layer, so that high emission intensity can be obtained. In addition, since the light is not reflected by the resin material, stable light emission can be obtained over time, and the reliability at the time of measuring element characteristics can be improved.

According to the second aspect of the present invention, the portion having a width of about 0.5 to 5 mm at the peripheral portion of the wafer has a poor yield. By using it for positioning, the wafer can be used more effectively.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on specific embodiments. FIG. 1 shows a light emitting device 10 made of a GaN-based compound semiconductor formed on a sapphire substrate 11.
FIG. 2 is a schematic cross-sectional configuration diagram of No. The substrate 11 is formed in a square having a side of about 2 inches. On this substrate 11, a buffer layer 12 made of aluminum nitride (AlN) having a thickness of about 25 nm is provided, on which a silicon (Si) doped
High carrier concentration n ⁺ layer 1 of GaN with a thickness of about 4.0 μm
3 are formed. On this high carrier concentration n ⁺ layer 13, a cladding layer 14 of about 0.5 μm in thickness made of Si-doped n-type GaN is formed. And the cladding layer 14
A light emitting layer 15 having a multiple quantum well structure (MQW) in which barrier layers 151 made of GaN with a thickness of about 35 ° and well layers 152 made of Ga _0.8 In _0.2 N with a thickness of about 35 ° are alternately stacked on the substrate. Have been. The barrier layer 151 has six layers, and the well layer 152 has five layers.
Layer. On the light emitting layer 15, a cladding layer 16 of p-type Al _0.15 Ga _0.85 N with a thickness of about 50 nm is formed. Further, on the cladding layer 16, a film thickness of about 1
A contact layer 17 of 00 nm is formed.

A light-transmissive electrode 18A is formed on the contact layer 17 by metal evaporation, and the electrode 18A is formed on the n ⁺ layer 13.
B is formed. The translucent electrode 18A is made of about 15 ° of cobalt (Co) bonded to the contact layer 17 and about 60 ° of gold (Au) bonded to Co. The electrode 18B is made of vanadium (V) having a thickness of about 200
It is made of μm aluminum (Al) or Al alloy.
On a part of the electrode 18A, an electrode pad 20 made of Co or Ni and Au, Al, or an alloy thereof and having a thickness of about 1.5 μm is formed. On the back surface of the substrate 11, a metal layer 10 of aluminum (Al) having a thickness of about 200 nm is formed.

Next, a method for manufacturing the light emitting device 100 will be described. The light emitting device 100 was manufactured by vapor phase growth by metal organic chemical vapor deposition (hereinafter abbreviated as “MOVPE”). The gases used were ammonia (NH ₃ ), carrier gas (H ₂ , N ₂ ), trimethylgallium (Ga (CH ₃ ) ₃ ) (hereinafter referred to as “TMG”), and trimethylaluminum (Al (CH ₃ )).
₃ ) (hereinafter referred to as “TMA”), trimethylindium (In
(CH ₃ ) ₃ ) (hereinafter referred to as “TMI”), silane (SiH ₄ ) and cyclopentadienyl magnesium (Mg (C ₅ H ₅ ) ₂ ) (hereinafter “CP
₂ Mg ”). First, a single crystal substrate 11 having an a-plane as a main surface, which has been cleaned by organic cleaning and heat treatment, is subjected to MOVPE.
The susceptor is mounted on the reaction chamber of the apparatus. next,
The substrate 11 was baked at a temperature of 1100 ° C. while flowing H ₂ into the reaction chamber at normal pressure. Next, the temperature of the substrate 11 was lowered to 400 ° C., and H ₂ , NH ₃ and TMA were supplied to form the AlN buffer layer 12 to a thickness of about 25 nm.

Next, the temperature of the substrate 11 is maintained at 1150 ° C.
Supplying H ₂ , NH ₃ , TMG and silane, the film thickness is about 4.0 μm,
High carrier concentration n composed of GaN with electron concentration of 2 × 10 ¹⁸ / cm ^3
+ Layer 13 was formed. Next, the temperature of the substrate 11 is maintained at 1150 ° C., and N ₂ or H ₂ , NH ₃ , TMG, TMA and silane are supplied to form a GaN film having a thickness of about 0.5 μm and an electron concentration of 1 × 10 ¹⁸ / cm ³ . Was formed. The above cladding layer 1
After the formation of No. 4, N ₂ or H ₂ , NH ₃ and TMG were supplied to form a barrier layer 151 of GaN having a thickness of about 35 °. Next, N ₂ or H ₂ , NH ₃ , TMG and TMI were supplied to form a well layer 152 of Ga _0.8 In _0.2 N having a thickness of about 35 °. Furthermore, the barrier layer 151 and the well layer 152 were formed under the same conditions for four periods, and the barrier layer 151 made of GaN was formed thereon. Thus, the light emitting layer 15 having the MQW structure having five periods was formed.

Next, the temperature of the substrate 11 is maintained at 1100 ° C.
Supplying N ₂ or H ₂ , NH ₃ , TMG, TMA and CP ₂ Mg, a film thickness of about 50 nm, p-type Al _0.15 Ga doped with magnesium (Mg)
_A cladding layer 16 of _0.85 N was formed. Next, the temperature of the substrate 11 is maintained at 1100 ° C., and N ₂ or H ₂ , NH ₃ , TMG and CP ₂ Mg are supplied to form a p-layer doped with Mg with a thickness of about 100 nm.
A contact layer 17 made of type GaN was formed. Next, an etching mask is formed on the contact layer 17, the mask in a predetermined region is removed, and the contact layer 17, the cladding layer 16, the light emitting layer 15, the cladding layer 14, and the n ⁺ A part of the layer 13 is etched by reactive ion etching using a gas containing chlorine, and n ⁺
The surface of layer 13 was exposed. Next, in the following procedure, n ⁺
An electrode 18B for the layer 13 and a translucent electrode 18A for the contact layer 17 were formed.

(1) A photoresist is applied, a window is formed in a predetermined region on the exposed surface of the n ⁺ layer 13 by photolithography, and the window is evacuated to a high vacuum of the order of 10 ⁻⁶ Torr or less.
Vanadium (V) having a thickness of about 200 ° and Al having a thickness of about 1.8 μm were deposited. Next, the photoresist is removed. Thereby, electrode 18B is formed on the exposed surface of n ⁺ layer 13. (2) Next, apply photoresist uniformly on the surface,
By photolithography, the photoresist on the electrode formation portion on the contact layer 17 is removed to form a window. (3) After evacuation to a high vacuum of the order of 10 ⁻⁶ Torr or less on the photoresist and the exposed contact layer 17 using a vapor deposition apparatus, a Co film having a thickness of about 15 mm was formed. About 60
A film of Au is formed.

(4) Next, the sample is taken out of the vapor deposition device,
Co, Au deposited on photoresist by lift-off method
Is removed, and a translucent electrode 18A is formed on the contact layer 17. (5) Next, in order to form a bonding electrode pad 20 on a part of the translucent electrode 18A, a photoresist is uniformly applied, and a photoresist is applied to a portion of the electrode pad 20 where the photoresist is formed. Open the window. Next, Co or Ni and Au,
Al or an alloy thereof is deposited to a film thickness of about 1.5 μm by vapor deposition, and Co or Ni and Au, Au deposited on the photoresist by a lift-off method in the same manner as in the step (4).
The electrode pad 20 is formed by removing the film made of l or an alloy thereof. (6) Thereafter, the sample atmosphere is evacuated with a vacuum pump, and O ₂ gas is supplied to a pressure of 3 Pa.
The contact layer 17 and the cladding layer 16 are heated to 50 ° C. for about 3 minutes to reduce the resistance of the p-type contact layer 17 and the cladding layer 16.
7 and electrode 18A, n ⁺ layer 13 and electrode 18
Alloying with B was performed. Thus, the metal layer 1
A wafer without zeros is formed.

Next, the formation of the metal layer 10 and the separation of the wafer will be described with reference to FIGS. First, as shown in a schematic cross-sectional view in FIG. 3, dicing is performed along a dicing line (not shown) of the wafer 200 using a blade 40 to reach a depth of about 15 μm from the electrodes 18A and 18B to the substrate. Then, a separation groove (first groove) 21 is formed (first step). Next, the substrate 1 is
1 is polished to make the substrate 11 thinner (second
Process). Thus, the cross-sectional configuration shown in FIG. 4 is obtained.

Next, as shown in FIG. 2A, in the wafer 200, a region B of about 0.5 to 5 mm width around the back surface 11b of the substrate 11 is masked to form aluminum (Al). Is deposited to form a metal layer 10 having a thickness of about 200 nm (third step). Thus, the cross-sectional configuration shown in FIG. 5 is obtained. Next, the wafer 200 is divided into four wafers 201.
If the wafer 201 is viewed from the metal layer 10 side, as shown in FIG. 2B, the structure is such that the metal layer 10 is not formed in the region B on two adjacent sides of the peripheral portion. Hereinafter, a description will be given using the wafer 201 as an example, but the same processing is performed on the other three wafers 202 to 204. When the warpage of the wafer 200 is large, the wafer 200 can be similarly divided from the first step after dividing it into four parts.

FIG. 2B is an enlarged view of a portion A in FIG.
(C). As shown in FIG. 2C, 1 to 10 elements and the separation groove 21 can be visually recognized from the metal layer 10 side through the non-formation region B. Since the region B is formed on two sides of the peripheral portion, the separation grooves 2 in two orthogonal directions can be visually recognized. Next, an adhesive sheet 24 is adhered on the electrode pad 20 to obtain the configuration shown in FIG. Next, scribing is performed using a scriber along the separation groove 21 from the metal layer 10 side to form a scribe line 25 (fourth step). FIG. 7 shows a cross-sectional configuration in this state. Next, the wafer 201 is braked by applying a load to the wafer 201 using a roller (fifth step), and the configuration of FIG. 1 described above is obtained.

As described above, the back surface 11b of the substrate 11
The metal layer 10 is formed in the peripheral portion except for the region B on two adjacent sides, so that the region B is separated from the separation groove 2.
1 can be recognized, scribing from the metal layer 10 side becomes possible, and the element 100 in which the metal layer 10 is formed on the back surface 11b can be obtained. Further, since the formation of the metal layer 10 is performed before the adhesion of the adhesive sheet 24, the metal layer 10 can be formed by heating by vapor deposition, and the adhesion between the back surface 11b and the metal layer 10 can be improved. This reduces the amount of chipping during scribing. Further, since the metal layer 10 has a higher thermal conductivity than the sapphire substrate 11, heat generated during scribing can be radiated well through the metal layer 10, and the amount of wear of the scriber cutting blade can be reduced. Further, in the light emitting element 100, light traveling toward the substrate 11 is favorably reflected by the metal layer 10 formed on the back surface 11b, so that light extraction efficiency from the electrodes 18A and 18B is improved, and the light emission intensity is improved. Can be enhanced. Further, since the metal layer 10 does not deteriorate with time, it is possible to obtain stable light emission with time, and to improve the reliability at the time of measuring element characteristics.

In the above embodiment, the metal layer 10 made of Al having a thickness of about 200 nm is provided by vapor deposition. However, the metal constituting the metal layer 10 may be of any type, and has a thickness enough to reflect light. Just do it. Further, the metal layer 10 may be formed using a method other than the vapor deposition. In the above embodiment,
Although the separation groove 21 was formed to a depth of 15 μm,
It may be in the range of m. The light emitting layer 15 of the light emitting element 100 has the MQW structure, but a single layer made of SQW, Ga _0.8 In _0.2 N, or the like, or other quaternary or ternary AlGaInN having an arbitrary mixed crystal ratio.
It is good. Although Mg is used as the p-type impurity, a Group 2 element such as beryllium (Be) and zinc (Zn) can be used. Further, the present invention can be used not only for a light emitting element such as an LED, but also for a light receiving element.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a structure of a GaN-based compound semiconductor light emitting device according to a specific example of the present invention.

FIG. 2 is a schematic plan view showing a configuration of a wafer of a GaN-based compound semiconductor light emitting device according to a specific example of the present invention.

FIG. 3 is a schematic view showing a first step in a method for forming a GaN-based compound semiconductor light-emitting device according to a specific example of the present invention.

FIG. 4 is a schematic view showing a second step in the method for forming a GaN-based compound semiconductor light-emitting device according to a specific example of the present invention.

FIG. 5 is a schematic view showing a third step in the method for forming a GaN-based compound semiconductor light emitting device according to a specific example of the present invention.

FIG. 6 is a schematic view showing a state in which an adhesive sheet is stuck on an electrode pad in the method of forming a GaN-based compound semiconductor light emitting device according to a specific example of the present invention.

FIG. 7 is a schematic view showing a fourth step in the method for forming a GaN-based compound semiconductor light-emitting device according to a specific example of the present invention.

FIG. 8 is a schematic cross-sectional view showing a state in which a conventional GaN-based compound semiconductor light emitting device is fixed on a lead frame.

[Explanation of symbols]

Reference Signs List 10 metal layer 11 sapphire substrate 12 buffer layer 13 high carrier concentration n ⁺ layer 14, 16 clad layer 15 light emitting layer 17 contact layer 18A p electrode 18B n electrode 20 electrode pad 21 separation groove 24 adhesive sheet 25 scribe line 100 light emitting element

Claims (2)

[Claims] 1. A method of manufacturing a gallium nitride-based compound semiconductor device in which each of positive and negative electrodes is provided on the same side, comprising: forming a substantially rectangular wafer having a gallium nitride-based compound semiconductor formed on a substrate; Cut to a predetermined depth from the side,
A first step of forming a first groove, a second step of polishing the back surface of the substrate after the first step, and thinning the substrate, and after the second step, Forming a metal layer in a region excluding at least two adjacent sides of a peripheral portion of the back surface of the substrate;
A fourth step of visually recognizing the first groove from the metal layer side via the peripheral portion and scribing along the first groove; and And a fifth step of breaking the wafer and separating the wafer into individual devices, the method comprising the steps of: 2. The method according to claim 1, wherein the width of the peripheral portion is about 0.5 to 5 mm.